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Aemb04
Tinkerer
Username: Aemb04
Post Number: 5
Registered: 04-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 16, 2013 - 04:18 am: | 
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Hello, I have just bought a Praktica IV off of ebay, the camera is fine but the lens a CARL ZEISS JENA TESSAR 50MM 2.8 (8 BLADES)(aluminium body type)is very hazy with fungus(it smells very musty). Does anyone know how to take one of these apart so as to clean the internal lenses. thanks for any help. |
Jdvores
Tinkerer
Username: Jdvores
Post Number: 5
Registered: 04-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 01, 2013 - 09:58 pm: |
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If only the front element looks fungusy, you need a lens spanner and you need to take off the ring with the nameplate. There might be another ring underneath that and then the lens element falls out. Remember which way it went and put it back after cleaning. If it's the rear element, I'm not as sure. If you have to take apart the whole thing, try and find a guide online before you screw up the helicoids. They're hard to put back together so that it focuses properly again.
Here's a sight I found just by googling - http://oomz.net/tessar/
Maybe it'll help. |
Prasanna
Tinkerer
Username: Prasanna
Post Number: 97
Registered: 10-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 02, 2013 - 05:48 am: |
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I found that one need not take out the front element unless in the particular sample the front element is separate as a single piece of glass. Usually, these are sealed as the front group in one cylinder and the rear group in another, with the aperture in between. So one can unscrew the rear group and clean both surfaces, as well as the rear surface of the front group by opening the aperture wide. The fungus or dirt occurs mostly in the outer surfaces of each group. Also be careful while cleaning the helical and try to refrain from pulling out the helical mount. If you do, then mark the position in which it enters the thread. There are usually six positions in which the thread will enter. Only one of them will focus to Infinity and the full range. If you miss that it will be a long process of trial and error. Not impossible but cumbersome/tedious. Some times it works as a good lesson too.  |
Aemb04
Tinkerer
Username: Aemb04
Post Number: 7
Registered: 04-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 08, 2013 - 08:40 am: |
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Hello thanks for the replies, I removed the entire lens assembly from the body by unscrewing the main locking ring, I then unscrewed the rings holding the rear lens in place & gave this a good clean then removed the front element & cleaned both of these lenses, put it all back together & whilst I was at it dripped some lighter fluid into the focusing mechanism to loosen it then a few drips of Ballistol gun oil to re-lube it. I'm not sure what you mean when you talk about the helical mount (are these the rear rings which I had to unscrew to remove the back elements) anyway it all seems to work OK now I think. |
Clie
Tinkerer
Username: Clie
Post Number: 2
Registered: 06-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 09, 2013 - 07:49 pm: |
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How did you remove the front lens assembly? Does the name plate just twist off? |
Jdvores
Tinkerer
Username: Jdvores
Post Number: 13
Registered: 04-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, June 09, 2013 - 09:23 pm: |
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Yes. I use either a piece of rubber (if it doesn't have notches for a spanner to go into), or a spanner, if it does have the notches for it. Some of my Carl Zeiss Jena lenses have two nameplates, and one has the notches and the other doesn't.
Aaemb04 - the helicoid is the threaded part that moves the elements in and out of the lens body to focus. It's usually covered in grease and is hard to put back together the right way [chances are, you won't focus properly.] |
Aemb04
Tinkerer
Username: Aemb04
Post Number: 8
Registered: 04-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, June 10, 2013 - 04:50 pm: |
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Hello Clie, I just used my fingers to unscrew the front name plate which goes down into the front of the lens like a cone shape, you may have to use a piece of rubber to grip it if its stuck. Behind this you then have another locking cone shaped ring which you will need a lens spanner to undo (got mine on ebay for £12). Once this is removed the front element can be taken out.
Thanks Jdvores for the explanation about Helicoids . |
Clie
Tinkerer
Username: Clie
Post Number: 3
Registered: 06-2013
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 11, 2013 - 04:43 pm: |
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It worked! I had to buy a new rubber stopper. I used an existing one, and couldn't move the name plate - guess it lost it's grippiness due to age.
There are 3 screws behind the plate, and once I remove that, the lens was easy to remove. I have a sparkling clear lens now :-) Thanks for the advice.
BTW mine is the Zebra version of the Jena 50mm f2.8 |
